if you’re using bash as your shell, then you should be able to type a tab character like so: press ctrl-v, then ctrl-i. though bash will appear to have skipped ahead several spaces, merely the one (tab) character has been typed.
Pressing tab in bash usually starts the tab completion feature which means that entering a literal tab character is not possible this way. Today I needed to enter a literal tab character and it turns out that you can do this in bash by pressing ctrl-v followed by ctrl-i 🙂